1. Field of the Invention
The present invention relates to an optical disk recording and/or reproduction device performing recording and/or reproduction of information for optical disks such as CD (Compact Disk) and DVD (Digital Versatile Disk).
2. Description of the Related Art
Conventionally, there have heretofore been known optical disk recording and/or reproduction devices that carry out the recording and/or reproduction of information by means of an optical head known as an optical pickup for optical disks such as CD and DVD, where information recording tracks are formed in a shape of concentric circles or a spiral shape. The optical pickup is constructed such that it converges and irradiates light from a semiconductor laser, etc. onto an optical disk via an objective lens, receives the reflected light of the light irradiated onto the optical disk, outputs a corresponding electric signal, and is moved in the radial direction of the optical disk.
The optical disk recording/reproduction device carries out the recording and/or reproduction of information for the optical disk by converging and irradiating light from the optical pickup onto the recording tracks of optical disk while moving the optical pickup to a defined position on the optical disk and rotating the optical disk.
In the reproducing information from the optical disk, first, a convergent point of light irradiating from the optical pickup is focused (focused-on)/(focus led-in) so that it is located on the optical disk surface and further tracked on (track led-in) so that the focused light is located on a recording track. Such focusing-on and tracking-on are carried out by moving the objective lens in a direction perpendicular to the optical disk surface and a direction perpendicular to the recording track in accordance with electric signals output from the optical pickup. At this time, pits formed on the optical disks are detected based on the electric signal output from the optical pickup in the focused-on and tracked-on state, by which information is read and reproduced from the optical disk. The recording of information onto the optical disk is carried out by forming the pits on the recording tracks of optical disk with the light converging and irradiating from the optical pickup onto the optical disk.
Usually, information showing the recorded contents of optical disk, information of an operational program, etc. are recorded on the inner-most side of recording tracks in an optical disk exclusively for reproduction where music and images are pre-recorded. This information is referred to as the TOC (Table of Contents), and the information is also sequentially recorded from the inner-most side of recording tracks in a case of an optical disk capable of recording information on the user side.
Therefore, for example, when the optical disk is mounted to the main body of optical disk recording/reproduction device, it performs the initial operation of reading information (TOC, etc.) recorded on the inner-most side of optical disk, determines the type and recording contents of optical disk based on information read by this initial operation, and controls subsequent information recording and reproduction operations. In this initial operation, light from the optical pickup is focused on and tracked on at a defined initial position (re-zeroing position) which is given some margin and becomes peripherally only a little farther out than the inner-most side of the recording tracks. The most inward position of the recording tracks is defined by making the optical pickup contact with a fixed mechanical switch provided in the optical disk recording/reproduction device.
In this initial operation, when there is only a little information recorded at the inner-most side of the optical disk, tracking on (track-leading in) sometimes cannot be accomplished even if the focusing can be done. To solve this problem, a technique has been proposed in which an optical pickup is moved from a re-zeroing position inward in the focused-on state and the movement of optical pickup is stopped when a normal pit cycle (period) is confirmed has been proposed (reference Japanese Laid-Open Patent Publication No. 2003-263755).
In the above-mentioned conventional optical disk recording/reproduction device, when a recorded optical disk is mounted to a device on the user side and there is only an extremely small amount of information recorded on the optical disk, the recording position becomes more inward than the re-zeroing position where light from the optical pickup is focused in the initial operation, and the optical pickup becomes encounters an (unreadable) error. For example, when a user records a short article or data of one photo on CD-R, the data is received on one to several recording tracks at the inner-most side of optical disk. In such a case, pits are frequently not formed in the re-zeroing position where the optical pickup is focused. Therefore, the disk cannot be tracked-on even if it should be. Consequently there is a drop in focusing and the recorded information cannot be read. When there is a drop in focusing, the focusing on operation is re-run and retried many times, but the position of optical pickup does not change, and in many cases the information cannot be read, even if retried.
Accordingly, the optical pickup is moved inward (or outward) to search tracks where a small amount of information is recorded if the information is not read by the optical pickup stopped in the re-zeroing position. In the technique of the above-mentioned reference, when normal reading cannot be accomplished in the re-zeroing position, the optical pickup is moved from the re-zeroing position inward in the focused-on state, and when a normal pit period can be confirmed, the movement of optical pickup is stopped.
However, when the information on the optical disk surface is extremely small, at from one to several tracks, as described above, even if the existence of information is detected based on the analysis of an output signal (RF signal, track cross signal, etc.) from the moving optical pickup and the optical pickup is braked to a stop at the detected time, the optical pickup stops at the position after passing tracks where the information already exists. Once the optical pickup has passed the tracks and pits are not formed in the stop position, an error occurs. To resolve this problem, the moving velocity of the optical pickup must be lowered, causing other problem that the time required for an information search extends.
Moreover, in the technique shown in the above-mentioned reference, the optical pickup is moved while confirming the pit period, therefore the optical pickup must be moved for a specified or greater distance in order to grasp the period of pits, and whether tracks recorded with information exists is determined afterward for a part where movement has ended. Accordingly, when the quantity of information on the optical disk is extremely small, even if the existence of information is detected and the optical pickup is braked to a stop, the optical pickup frequently passes the part where information already exists (information recording area) in the stopping position, the information is not read, and the possibility of error is high.